
Originally Posted by
Elusive
It's also worth noting that Microsoft share achievement data with game developers. This means that after a game has sold, they can examine how many people played the game to completion as opposed to getting bored and playing something else (hence games having achievements for finishing levels 1, 2, 3, 4, 5...), the time between getting the first achievement and the previous allows you to judge whether people are playing in short chunks or steamrolling over a weekend, and so on, or even if people are bothering to configure their starting character or whatever.
Some games do this in the background anyway; for example, Mass Effect 2 and other EA games. Naturally Halo also does this, to generate all the lovely stats and user content on bungie.net.